In many industries, workers are required to perform various functions where the ambient air contains toxic or irritating vapors or particles. In such a situation, the workers need personal air filtration devices, popularly called "gas masks", for removing harmful substances from their breathing air. Various solid chemical filtration media are known in the art for use with gas masks. Activated charcoal and silica gel are among those substances frequently used for this purpose. However, solid filtration media present a problem to the user. Specifically, the filtration medium used in a gas mask eventually becomes saturated with contaminants from the filtered air and, therefore, the medium must be removed and replaced. The required periodic removal and replacement of a solid filtration medium is expensive and can be difficult to accomplish. The use of a liquid filter media or more specifically, a water filter medium, largely eliminates the problems discussed above associated with solid air filters for gas masks because, in most cases, water is readily available and can be easily and inexpensively obtained for replacement purposes.
The use of a liquid as a filtration medium for impurities in gases is well known in the prior art. More specifically, it is also known to use water to filter impurities from air to be inhaled. For example, U.S. Pat. No. 3,703,179 shows a smoke filtering device including a mouthpiece connected to a canister partially filled with water. A cigarette is inserted in an inlet to the cannister so that inhalation at the mouthpiece causes smoke to flow into the canister, through the filtering water and out through the mouthpiece. Similar devices are shown in U.S. Pat. Nos. 183,626, 1,826,331, and 3,209,765. Each of these devices is portable and operates properly when carried about with the user provided that the device is continuously oriented in approximately an upright position. It should be noted that if the orientation of any of these devices significantly deviates from the upright position, water flows out through the mouthpiece and/or out through the inlet port thereby gagging the user or extinguishing the tobacco. Thus the user could not bend head down over a work bench or lie on his side in a mine tunnel without spillage.
In U.S. Pat. No. 2,088,720 to Poliniak of Aug. 3, 1937 and German Pat. 959619 to Drager of Mar. 7, 1957, liquid filter gas masks are disclosed but with no means for preventing liquid from leaking into the face mask when inverted. In U.S. Pat. No. 1,196,539 to Goldberg of Aug. 29, 1916 a liquid filter gas mask is disclosed in which an immovable tapered guard, with a restricted opening is stated to prevent splash but no valve means is provided to permit simple construction with unrestricted openings capable of positive closing to prevent leakage.
Additionally, complex gas filtration devices having a liquid filter medium are used in many industrial chemical processes. One such apparatus is disclosed in U.S. Pat. No. 3,733,782. Such devices however, are stationary and intended for use only in one orientation.
It is therefore desirable to provide a portable air filtration unit which is secured to the user and easily carried about by him and which continues to function properly over a wide range of orientations since the user is likely to assume a variety of different positions while still needing to breathe filtered air. In addition, the device should provide filtered air to the nose and mouth of the user so that his breathing remains unencumbered and natural.